This invention relates generally to systems for monitoring the presence or absence of a patient in or from a hospital bed, patient chair or the like and more particularly concerns monitoring systems having programmable capability to tailor the system functions to meet the needs of specific hospital or short term care monitoring applications.
Presently known monitoring systems, such as those described in earlier U.S. Pat. Nos. 4,484,043 and 4,565,910, have serious limitations of function and operating capability. They make no provision for ready interfacing with the variety of nurse call station configurations in different and even in the same hospital facilities. They may require the manual operation of on/off switches to activate the monitoring process. Once activated they must then be shut down completely to enable a nurse to move a patient and then manually switched on to reactivate the device after return of the patient. They are not locally modifiable by the monitoring staff to accommodate the needs of a particular patient and/or environment. They generally offer no selection of tonal variations in their audio alarm and no selection of time delay increments required to trigger their alarm modes. Furthermore, even in those systems which do permit some time delay adjustment, the system remains in the last time delay mode to which it was adjusted until an active readjustment of the selected delay is made. Consequently, failure to actively adjust the time delay from a previously selected increment could have an undesirable impact on a different patient or environment. A further problem encountered in present monitoring systems is that they employ their on/off switch controls in such a manner that loss of power or inadvertent disconnection from the nurse call station does not cause an alarm. Therefore, the monitoring staff has no assurance that a patient is actually being monitored without repetitive local inspection to assure that the system is properly connected and operable.
It is, therefore, one of the primary objects of this invention to provide a system which is suitable to monitor short term and/or hospital care patients. Another object of this invention is to provide a patient monitoring system which can be readily interfaced with a variety of nurse call station configurations. Still another object of this invention is to provide a patient monitoring system which is programmable on-site by monitoring personnel to adapt the system to each specific patient and environment. It is also an object of this invention to provide a patient monitoring system which is activated by initial pressure on a sensor device for a predetermined continuous time period rather than by the use of on/off switches. A further object of this invention is to provide a patient monitoring system which can be temporarily deactivated to a "hold" mode by use of a single hold/reset control on the unit and which will be automatically reactivated to a "monitor" mode when the patient is returned to the system for a predetermined continuous time period. Another object of this invention is to provide a patient monitoring system which can be immediately activated to override a predetermined delay so as to prevent a quick moving patient from defeating the system. Yet another object of this invention is to provide a patient monitoring system in which disconnection of the system from the sensor device, from power or from the nurse call station will result in a failsafe alarm. A further object of the present invention is to provide a patient monitoring system which, in its programmable functions, includes variations of type and volume of alarm tones. It is also an object of this invention to provide a patient monitoring system which permits active selection of time delay increments required before triggering of an alarm and also automatically defaults to a "normal" preselected time delay if a different delay period is not actively selected. And it is an object of this invention to provide a patient monitoring system which provides on-site ability to adapt the system to any of a variety of nurse call station configurations.